Lamellar structures are microstructures composed of fine, alternating layers of different materials in the form of lamellae. Lamellar silica (e.g., phyllosilica) and/or aluminosilicates are an important class of porous materials because their interlayer surfaces can be organically modified through ion-exchange, adsorption, and/or direct derivatization. These lamellar materials can also be hybridized with polymers to produce nanocomposites with properties such as, thermal and ultraviolet resistance, dimensional stability, and enhanced mechanical characteristics. However, due to the difficult dispersion behavior of the filling polymer, research on the exfoliation of the layered silica in polymers and intercalation of polymers between layered silica is increasing rapidly.
Clay minerals are hydrous aluminosilicates consisting of stable films only a few nanometers in thickness and with lateral dimensions on the order of 1 μm. Because of their anionic characteristics, cationic organic molecules can be intercalated and immobilized on the surface of clay materials. However, a drawback to this approach is the difficulty in avoiding molecular aggregation, especially in high loading conditions.
Zeolites are aluminosilicates with periodic three-dimensional frameworks having various chemical compositions. One disadvantage in their use is their limited pore size, which limits larger molecular entities from entering the voids of these materials. Zeolites are also typically negatively charged due to the replacement of Si+4 by Al+3 and, thus, they are not suitable for many adsorption, separation, and catalytic processes. Yet another significant disadvantage of zeolites stems from the presence of Al+3 or other ions within their layered framework, which typically leads to aggregation of their sheets.
Researchers have synthesized lamellar MCM-50 with high surface areas, such as, for example, 1000 m2/g. Lamellar MCM-50 can be crystallized in a solution of surfactants just over the critical micelle concentration (“CMC”) point, defined as the concentration of surfactants above which micelles are spontaneously formed. However, the surfactants used for crystallization are relatively costly and their recovery can result in collapse of the lamellae.
Therefore, a new, more economical method for formation of silica compositions using low surfactant concentrations is necessary.